The present invention relates to phytocannabinoids for use in the treatment of a breast cancer. In a first embodiment the invention relates to an oral presentation of tetrahydrocannabinol (THC) for use in the treatment of aggressive breast cancer, characterised by overexpression of the Her2 gene. In a second embodiment the invention relates to the phytocannabinoid cannabidiol (CBD) for use in the treatment of aggressive breast cancer, characterised by overexpression of the Her2 gene. In a third embodiment the invention relates to the combination of the phytocannabinoids tetrahydrocannabinol (THC) and cannabidiol (CBD) for use in the treatment of breast cancer or to treat, prevent or to reduce the risk of a cancer metastasising.
